This invention relates to a brake for paper roll bearing shaft in a paper roll support frame of web feeder for rotary press.
A brake for paper roll bearing shaft provided on each paper roll support arm of a radial arm member mounted on a rotating shaft in a paper roll support frame of web feeder for rotary press is usually called a center brake, and its braking force is adjusted fine according to a detection signal from a tension detector provided in a travelling path of web. Then, with reference to a set of paper roll bearing shafts disposed opposite each other, the center brake operates so as to deliver the web during the period from the point in time when the paper roll on the bearing shafts is pasted to the point in time when the next paper roll is pasted through a delivery of the web and then the web is cut to terminate the web delivery, thus braking the bearing shafts, but it does not operate in order to install a paper roll and prepare for web pasting, after the termination of the web delivery and while a new paper roll is installed and then the new paper roll is pasted to the preceding one, thus releasing the bearing shaft rotation from being braked.
Now, therefore, in a prior art center brake working on air pressure, a valve in a pneumatic circuit for actuating and releasing the rotation braking of the paper roll bearing shafts at every paper roll support arms is operated manually by workers or mechanically by a device disclosed, for example, in Japanese Utility Model Publication No. 52215/1981. The device works on gravity, mounted on the turning paper roll support arms and thus operates the valve according to operation of a rod pivoting on a weight. However, since gravity works in one direction at all times, the weight becomes effective or ineffective for the rod to operate the valve depending on a turning phase of the paper roll support arms, therefore a desired braking operation is obtained by properly relating a turning phase of the paper roll support arms with a braking cycle of the paper roll bearing shafts.
In the foregoing prior art, a manual operation of workers entails troublesome valve operation and cannot prevent an erroneous operation perfectly. Then, in the case of gravity utilization, since the rod is pivoted only on a weight according to the turning phase of the paper roll support arms, a dependable valve operation cannot be expected. Further, an opening/closing cycle of the valve is restricted by the turning phase of the paper roll support arms.